A clock circuit often includes a crystal oscillator for generating a clock signal. The crystal oscillator includes a crystal manufactured from a piezoelectric material to have a precise resonant frequency. Moreover, the frequency of the clock signal is the same as the resonant frequency of the crystal. As a result, the frequency of the clock signal has the same precision as the precision of the resonant frequency of the crystal.
Generally, the precision of a resonant frequency of a crystal increases as the resonant frequency of the crystal decreases. As a result, the precision of the frequency of a clock signal generated by the crystal oscillator including the crystal decreases as the resonant frequency of the crystal increases. Additionally, the size and cost of a crystal having a higher resonant frequency are higher than the size and cost of a crystal having a lower resonant frequency. As a result, the size and cost of a clock circuit containing the crystal having the higher resonant frequency tends to be higher than the size and cost of a clock circuit containing the crystal having the lower resonant frequency. Moreover, some applications require two clock signals each having a precise frequency. In these applications, the clock circuit generates one of the clock signals based on a crystal having a lower resonant frequency and the other clock signal based on a crystal having a higher resonant frequency.
In light of the above, a need exists for an improved system and method of generating a clock signal based on a crystal. A further need exists for reducing the size and cost of a clock circuit that generates two clock signals each having a precise frequency.